Green, who was intervening in an argument between Brotherston and a former girlfriend, died in hospital two days later.

Brotherston's lawyer, Richard Neary, said Wednesday his client pleaded guilty because he didn't want the victim's family and friends to have to endure a trial.

"He did not want those people to have any lingering doubts or concerns that he was going to somehow try and escape responsibility for what happened to Mr. Green," Neary said.

"While my client never expected, intended or could even have imagined that the act of slapping Mr. Green would have the tragic consequences that it did, he fully acknowledges that he is guilty of manslaughter."

Neary also said Brotherston knows that a jail sentence of some length is a likely and appropriate outcome of his conviction.